Measurement of an object's dimensions has typically been accomplished in a manual fashion using fixed-length rulers, adjustable-length rulers (e.g., tape measures), plumb lines, hand levels and combinations thereof. Use of these various manual measurement tools becomes difficult and/or dangerous when object is large and/or irregular in shape, or is located in an environment that is limited in terms of accessibility or is inherently dangerous.
In general, oversized loads must be measured prior to their movement by any land, water, and/or air-based vehicle for reasons of safety, efficiency, etc. Oversized loads transported over land (e.g., by railroad, road travel, etc.) must be measured prior to being moved over a predetermined route in order to assure that the load can maintain safe clearance over the route. By way of illustrative example, this scenario will be explained for railway freight. In general, railway freight shipments that exceed a standard geometric envelope are deemed oversized and officially classified as “Dimensional” or “High-Wide-Loads” (HWLs). Each railroad typically has its own set of specifications for what is considered to be a HWL load. HWLs must be measured at points of origin and interchange points in route to their destinations to ensure that they can be safely transported over a particular rail line's route. Typically, several personnel are necessary for measuring a single oversized load.
The traditional method of measuring HWLs required personnel to either climb onto the load and/or use a ladder to physically measure the high points and wide points of the load. The typical tools used in the current measurement method include a tape measure, plumb line, carpenter's level, and variety of homemade tools to assist inspectors in measuring hard-to-reach high-wide points. Such manual measurements have a number of inherent limitations relative to accuracy, efficiency, standardization, documentation, and safety.
In terms of accuracy, there are a number of factors that contribute to measurement inaccuracies. For example, many HWLs have critical points that are difficult to reach. As a result, inspectors must often make multiple measurements to determine a single height or width at a critical point on the load. Recordation of these manual measurements can also be the source of mathematical and transcription errors. In addition, field measurements are currently referenced horizontally to the edge of the railcar and vertically to the deck of the railcar (which is then referenced vertically to one point on top of a rail and horizontally to a vertical projection of the railway car's centerline). This approach also makes the assumption that the center of a railcar is aligned with the centerline of the track. However, this assumption is not true in the vast majority of cases thereby leading to horizontal errors. Vertical errors arise because the current method assumes that the track is level and fails to account for uneven rail elevations. Further, the current method of measuring HWLs does not account for “humping” or “bellying” (positive or negative camber) of the railcar deck due to the weight of the load and/or the design of the railcar deck. Thus, the current method assumes that the railroad track is level and the deck of the railcar is also level. Since no track or car deck is perfectly level, inaccurate height and width measurement calculations are produced.
In terms of efficiency and safety, most HWLs require two or more people to make the measurements. The manual measurement method usually requires personnel to either climb onto the load and/or use a ladder to physically measure the high points and wide points. Often, a man-lift or bucket truck is required to reach critical positions on the load where dimensions are required. Climbing on the loads, positioning/repositioning ladders or bucket trucks are time-consuming tasks. Further, these pre-measuring steps expose personnel to trip/fall hazards on the deck of the railcar, slick surfaces during inclement weather, and overall difficulties in traversing loads due to the generally irregular shapes of HWLs. These combined inefficiencies of the current method also negatively affect overall rail yard operations. During the measurement process, “blue flag” protection is usually required which means the track where the load is being measured is closed. Moreover, if a ladder is used to measure the oversized load, it is often necessary to shut down adjacent tracks in addition to the track where the load is sitting. This negatively affects the railroad's ability to efficiently assemble and switch trains thereby delaying shipments. Additionally, a single measurement error could result in an inefficient routing of the load or a clearance deficiency resulting in a derailment, collision, property damage, environmental damage or even death.
In an effort to improve the accuracy, efficiency, and safety associated with measuring HWLs that are to be transported via railroad tracks, a laser-based dimensional object measurement method and system has been developed and is disclosed in U.S. Patent Publication No. 2013/0096875. Briefly, this reference discloses a method/system in which each of two targets is attached to a railroad track using a bar-like mechanism. The targets are positioned at each end of a railway car that is supporting a load (commodity) to be measured. A laser-based distance measuring device is positioned within line-of-sight of the targets and the load to be measured. The laser-based measuring device is used to measure vectors to the targets and vectors to positions on the load. The vectors to the targets are processed to generate horizontal and vertical references between the targets. The vectors to positions on the load are processed in order to generate dimensions of the load in relation to the horizontal and vertical references. While this system/method is a substantial improvement over the manual measurement method, it is predicated on an average top-of-rail height at a railroad track's centerline. However, most railroad tracks' left and right rails are not at the same elevation such that a load thereon is tilted side-to-side and/or front-to-back. For HWLs, this reality can lead to errors in a load's width or height that, in turn, can lead to an incorrect decision related to the load's ability to be safely transported over a particular rail line route.